Magnetic properties and magnetoimpedance effect in FINEMET/TiO₂/Fe₂₀Ni₈₀ composite ribbons

The impact of TiO₂ and Fe₂₀Ni₈₀ coating layer on roughness, magnetic properties, giant magneto-impedence (GMI) effect and dipole interactions of FINEMET/TiO₂/Fe₂₀Ni₈₀ composite ribbons were investigated systematically. The TiO₂ layer can effectively tune transverse magnetic structure and GMI ratio of composite ribbons. More TiO₂ coating layer thickness deteriorates the magnetic properties, and dipole interactions decrease owing to the distance between FINEMET ribbon and Fe₂₀Ni₈₀ layer increases. When the thickness of TiO₂ is 100 nm, composite ribbons exhibit small roughness of 8.5 nm, a large GMI ratio of 63% at 0.8 MHz, dipole field of 1.0 Oe, which is superior to other semiconductor composite ribbons. The variation in GMI ratio can be explained as the change of transverse permeability, and the decrease of magnetic dipole interactions can be explained as the change of distance between the FINEMET ribbon and Fe₂₀Ni₈₀ layer. The results show that the combination of semiconductor and magnetic materials can realize the miniaturization of magnetic sensing, and it has a guiding role in the development of GMI effect and magnetic interactions theory of composite materials.